The engine and travel speeds of vehicles controlled by human operators, e.g., passenger autos, trucks and the like, is often controlled (at least as to engine speed) by controlling the position of a foot-operated accelerator. Accelerator-based speed control works very well in those situations where the road is smooth and, consequently, the driver has no trouble maintaining a steady foot position. Such speed control is also preferred where the operator has relatively few manual tasks to manage and/or such tasks are required to be performed rather infrequently.
On the other hand, there are situations where foot-operated speed control (as a continuing mode of operation) is distinctly undesirable. An example is a crawler tractor which usually operates on rough, operator-jostling terrain. Under such conditions, it is well-nigh impossible for the operator to maintain a steady engine speed by foot control alone.
And operating a crawler tractor may impose other requirements. When used as an earthmoving machine (rather than as, say, merely a "drawbar" vehicle to pull a load), the operator must continually manipulate levers and/or pedals to turn the vehicle and operate its blade or bucket to move earth or to load it into a truck. Notwithstanding the manual and mental dexterity required to operate such a machine in this way, some operators do prefer to control engine speed by a conventional accelerator-like pedal. Others do not.
Rather, they prefer to run the engine at a much higher speed (so-called "high idle") by using a manually set throttle lever and depress a pedal to decrease engine speed. An advantage of such operation is that because of the elevated engine speed, the horsepower available from it is substantially greater than the horsepower available from a slowly-idling engine. Simply stated, the vehicle is able to perform more work faster but without the annoyance (as some see it) of having to continually maintain a pedal in a depressed position.
The improved engine throttle linkage provides either type of pedal arrangement in a way believed to be unique.